Fourth Amendment law regulates criminal investigations. Specifically, it regulates when and how the police can collect evidence to prove crimes beyond a reasonable doubt. Fourth Amendment law faces a recurring problem, though: The facts of crimes and the facts of investigations are constantly changing. The bad guys are constantly coming up with new ways to avoid being caught, and the cops are constantly coming up with new ways to catch them. As a result, Fourth Amendment law is constantly facing new facts to regulate. . . .

My argument is that there turns out to be a surprisingly common and surprisingly simple way that courts respond to this problem — and that response ends up explaining a remarkable amount of Fourth Amendment law. Courts respond to the new facts by trying to restore the old level of protection. If a new technology or practice increased government power, courts ratchet up Fourth Amendment protection to lessen government power. If a new technology or practice decreased government power, courts loosen protection to restore government power. The result is a correction mechanism. It’s kind of like the experience of driving over mountainous terrain: You add gas on the uphill and let off the pedal on the downslope, all in an effort to maintain constant speed. That’s what judges do when they come across new facts in Fourth Amendment cases.

. . . If you open a book on the Fourth Amendment and just start learning the rules, the rules seem almost random, as every fact pattern seems to have its own special treatment. But if you take a historical approach and see how each new fact pattern emerged and threatened the status quo, you can begin see the rules in each area as reflecting localized efforts to restore the status quo in light of what was then a new technology or practice.

As a descriptive theory, Professor Kerr’s analysis neatly explains the messy details of Fourth Amendment law, which is impressive. But Kerr attempts to justify the equilibrium-adjustment theory normatively as well. Intuitively, it seems strange to permit judges to wield constitutional provisions as a shield against any change to the status quo of governmental power. But if the point of search-and-seizure law is to balance the relationship between the state’s police power and individual rights, then maybe we should adjust the law as that balance shifts.

My concern is that Kerr’s approach, by defining Fourth Amendment law in terms of maintaining the status quo, assumes that the status quo is worth maintaining. In other words, judges, in Kerr’s view, don’t try to find the appropriate balance between police power and liberty, or the balance intended by the Framers, or the balance that best reflects modern American values, or whatever balance your preferred theory of constitutional interpretation maintains judges should be looking for. And even if the status quo is the perfect balance worth enshrining into law, can we simply assume that when reading the Fourth Amendment?